1. Field of the Invention
The present invention relates to an air bag system which is disposed in a vehicle and, in a vehicle collision, is used to restrain the head and bosom portion of an occupant with an air bag expanded and, in particular, to an air bag system which can adjust the internal pressure of the air bag to thereby expand the same according to the degree of the vehicle collision as well as according to the weight and sitting position of the occupant.
2. Description of the Related Art
Conventionally, as an air bag system which is used to restrain an occupant with an air bag expanded, there is known a system which adjusts the internal pressure of an air bag to thereby be able to expand the same according to the sitting position of the occupant, the degree of vehicle collision, and the like. In this type of air bag system, the degrees of collision, the sitting position of the occupant and the like are classified into stages according to predetermined boundary values, and the internal pressure of the air bag is adjusted according to the stages.
That is, there are set boundary values which are respectively used to check, for example, whether, as the sitting position of the occupant, a distance from the air bag folded to the occupant is less than 40 cm or not, or whether the acceleration in the collision is less than 70 Km/H or not, or whether the weight of the occupant is less than 50 Kg or not, or the like. And, the internal pressure of the air bag is adjusted in stages in accordance with whether the above-mentioned parameters exceed their respective boundary values or not.
However, in the above conventional air bag system, when the parameters are adjacent to these boundary values, for example, when the internal pressure of the air bag is adjusted in stages as low or high according to whether the weight of the occupant is less than 50 Kg or not, if the weight of the occupant is 49 Kg, then the occupant is restrained by the air bag expanded with a low level of internal pressure; and, if the weight of the occupant is 50 Kg, then the occupant is restrained by the air bag expanded with a high level of internal pressure. In this case, in spite of the fact that the weight difference is only 1 Kg, the occupant of 49 Kg is restrained with the low level air bag internal pressure. That is, in the conventional air bag system, there is still left room for improvement in restraining the occupant with the air bag properly.